Journal Issue: Proceedings of the Annual International Conference on Soils: Volume 12, Issue 1
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Short-Term And Long-Term Bioreactors For Acid Mine Drainage Treatment
Neculita, Carmen M.; Zagury, Gérald J.; Kulnieks, Viktors
Passive biological treatment of acid mine drainage (AMD) relies on sulfate-reducing bacteria (SRB) supported by a biodegradable organic carbon source. However, long-term treatment performance can be limited by the degradation rates of organic carbon available to SRB, and by low metal stability in spent reactive mixtures. The first part of this study focused on characterization of six natural organic materials and their short-term effectiveness in sulfate-reduction and metal removal from synthetic AMD. In the second part, long-term performance and metal precipitates in the reactive mixtures were assessed. Maple wood chips, sphagnum peat moss, leaf compost, conifer compost, poultry manure and conifer sawdust were analyzed in terms of their carbon and nitrogen content, as well as their easily available substances content (EAS). Single substrates and substrate mixtures were tested in a 70-day batch experiment (2-L reactors) and in an extended batch study for up to 350 days. Geochemical modeling and scanning electron microscopy (SEM) was used to assess the minerals present in the solid phase. The highest EAS content and the lowest C/N ratio suggested poultry manure would be the best substrate. Nevertheless, the lowest efficiency was found in the poultry manure reactor, whereas the mixture of three organic materials was the most effective. After 350 days, the mixture of organic carbon sources was still efficient for AMD treatment. SEM analysis of the solid phase indicated the presence of iron sulfides. Substrate characterization provided insight on organic carbon availability but did not elucidate their ability to promote sulfate-reduction and metal removal. Further research is needed to accurately predict long-term carbon availability and to assess the metal precipitates in spent reactive mixtures.
An Overview Of Occurrence And Evolution Of Acid Mine Drainage In The Slovak Republic
Slesarova, Andrea; Kusnierova, Maria; Luptakova, Alena; Zeman, Josef
At the present time acid mine drainage (AMD) belongs among the worst environmental problems associated with mining activity. At the beginning and in the middle of Twentieth Century the attenuation of mining activity in the Slovak Republic gave rise to extensive closing of deposits using wet conservation i.e. their flooding. The negative results of AMD activity can be observed mainly at localities after the mining of sulphide ores and raw materials containing sulphides. At the deposits Roznava, Pezinok and Rudnany the surrounding carbonate system is partly buffering the AMD evolution. During the last decade at the locality Sobov there was applied various remediation methods aimed at reducing the environmental impact of AMD but without marked success. The deposit of Smolnik represents from the point of occurrence and generation of AMD the classical example. All the area of deposit is markedly affected by AMD activity. The mine waters have pH 3.8, high concentrations of sulphates, Fe, Mn, Cu, Zn, Al, and are discharging straight in the stream Smolnik. In order to propose the effective and economically available method to prevent the negative influence of AMD at this locality it is necessary to understand the reasons of changes in evolution of mine water composition and real estimation of their long-time evolution. The article presents the results of monitoring of AMD quality at the locality of Smolnik in years 1986 – 2005. In order to better understand processes running at the locality there was also realized the geochemical modeling of AMD quality evolution during its gradual ascent of surface.
MASSDEP’s Evaluation Of Laboratory Performance Based On A Large VOC Double-Blind Study
Marra, R. Kendall; Fitzgerald, John J.
During 2004 and 2005, the Massachusetts Department of Environmental Protection (MassDEP) conducted a large double-blind laboratory evaluation study, involving 19 commercial laboratories that provide the majority of analytical support services to parties assessing and cleaning up hazardous waste sites in Massachusetts. A “double-blind” study is one in which a laboratory is unaware that they have been sent samples that contain known concentrations of contaminants. The study was undertaken by MassDEP as part of a multi-year/multi-component data enhancement effort, in order to obtain a direct, real world sense of data quality and reliability in its waste site cleanup program. MassDEP contracted with a well-known laboratory Proficiency Testing company to prepare test samples. To maintain the confidentiality of the study, the company set up mock consulting firms to send out samples and pay for analyses. Each laboratory was shipped a soil sample and groundwater sample spiked with measured concentrations of 5 common Volatile Organic Compounds (VOCs). This procedure was repeated on 3 different occasions -- in July, September, and November of 2004 -- at identical spiking concentrations. In addition to these 19 commercial laboratories, double-blind samples were also delivered to the MassDEP state analytical laboratory (the Wall Experiment Station), by an agency employee, under the pretense of being samples from a confidential enforcement case. MassDEP believes the results of this study are very encouraging. The vast majority of the laboratories evaluated were able to consistently quantify most analytes within 20% of the actual value. This excellent result is well within the most stringent acceptance criteria in use by the industry. In a few cases, false positive or false negative results were reported, particularly with respect to vinyl chloride in water, which is known to be a problematic analyte. MassDEP is conducting further review of analytical data generated by the study to attempt to determine the reasons for these results. Given these findings, MassDEP believes the public can have confidence in the integrity of the commercial laboratory community, and in the accuracy of the analytical data used to confirm cleanup of sites contaminated with Volatile Organic Compounds (VOCs), which are among the most pervasive and problematic pollutants at hazardous waste sites.
Treating Arsenic-Contaminated Soil At A Former Herbicide Blending Facility
Chowdhury, Ajit K; Stanforth, Robert R; Overby, Ross
Arsenic-contaminated soil at a Superfund site in Missouri was treated during 2005 using a ferric sulfate-based additive. Initial testing indicated that 20 percent Portland cement was needed to treat the soil; in contrast, only around 2 percent of the ferric sulfate additive was required. The exact dosage depended on the arsenic content of the soil. Arsenic screening using X-ray fluorescence (XRF) was used for the in-field determination of the dose required for each batch of soil. Varying levels of available iron in the soil was an additional factor in selecting the dose of treatment chemical. More than 70,000 tons were successfully treated and disposed, at an average chemical dose of 2 percent. The correlation of XRF arsenic data with wet compositional analysis, the relationship of available iron to arsenic ratio with TCLP-arsenic analysis, and the dosage-response for chemical treatment of soil comparing the bench-scale and full-scale treatment data are discussed.